1. Field
The following description relates to a compatible optical pickup and an optical information storage medium system using the same, and additionally, to a compatible optical pickup in which a single diffraction device is shared and used to divide light having a plurality of wavelengths and an optical information storage medium system using the same.
2. Description of the Related Art
In an optical pickup, a diffraction device for dividing light output from a light source into three beams is used to detect a tracking error signal by a three-beam method or a differential push-pull method. In a compatible optical pickup for compatibly operating a plurality of different kinds of optical information storage media, e.g., a Digital Versatile Disc (DVD) and a Compact Disc (CD), using different wavelengths by applying a 2-wavelength light source to the compatible optical pickup, if light output from the 2-wavelength light source is divided by a single shared diffraction device, the diffraction device may be formed in a structure in which a diffraction pattern for dividing light of a wavelength for a DVD is included in one side of the diffraction device and a diffraction pattern for dividing light of a wavelength for a CD is included in the other side thereof.
If light of, for example, the wavelength for a DVD is incident on the diffraction device, undesired noise light may be generated due to diffraction by the diffraction pattern for dividing light of the wavelength for a CD besides diffraction on the diffraction pattern for dividing light of the wavelength for a DVD and is incident to a light reception surface of a photo-detector for a DVD.
The noise light affects a detection signal of sub-light for a DVD, thereby affecting a tracking error signal.